During transportation in rail tank cars, pseudo-homogeneous solid/liquid suspensions tend to settle so that the solid particles are often much more densely concentrated near the bottom of the rail car tank than in other areas of the tank. If this slurry is not properly distributed prior to unloading, much of the solid may be left in the rail tank car after all of the liquid has been pumped out.
Known rail tank cars have included sparger systems to distribute these particles within the liquid. These sparger systems have included a vertical syphon tube coupled via a standard "tee" fitting to a sparger pipe located along a central axis of the rail tank car. However, rail tank cars including such known sparger systems employed by the assignee of this patent application have failed to effect a homogeneous distribution of the solid particles and have left residual tacky deposits of magnesium hydroxide. These deposits must be removed from the interior of the rail tank car and from the interior of the sparger pipe after unloading the slurry. Cleaning fluid (e.g. water for flushing magnesium hydroxide) is introduced into the vertical syphon tube under pressure and forced out through the openings in the sparger pipe to clean the system. However, due to the large pressure loss occurring at the "tee" fitting and the consequent maldistribution of the cleaning fluid along the array of sparger pipe openings, much residue is left within the rail tank car and within and on the sparger pipe 20. Thus an additional cleaning process is required in which personnel must enter the interior of the rail tank car. This process is time consuming, expensive and potentially dangerous to the personnel performing the operation. When required to enter the rail tank car to perform the cleaning operation, personnel are subject to several hazards including potential suffocation in an accidentally sealed tank car, drowning in liquid remaining in the tank car and injuries resulting from falls from atop or inside the tank car. Falls within the car may also damage the car itself or the sparger pipe. This is especially true when personnel enter the car carrying equipment. In addition, this cleaning operation increases the time required to return the rail tank car to use and usually wastes the material not unloaded with the slurry.
To prevent the back-flow of slurry into the sparger pipe, prior art systems have employed various means including reduced diameter nozzles to elastomeric check valves. However, these features increase the cost of the system as well as the cost of maintaining the system. Moving parts and reduced diameter nozzles add to the probability of clogging with tacky or lodged solids and the added fittings may fail releasing into the slurry broken pieces which can damage the pumps used in unloading. In addition, personnel must enter the rail tank car to service these components as they are located within the car.
Thus there is a need for a sparger system which reduces the amount of residue left in a rail tank car after a solid/liquid suspension has been unloaded and which allows the rail tank car and the sparger system to be quickly and effectively cleaned.
There is also a need for a sparger system which reduces the need for personnel to enter the rail tank car and which effectively distributes the solid particles throughout the slurry to form a pseudo-homogeneous solid/liquid suspension prior to unloading.